You DO realize that the definition of marriage has changed several times, right? Women are no longer property owned by their fathers until transferred into the possession of another Man. Being of different race no longer means you can't get married, either.
Furthermore, we re-define words all the time in the computer field. Think about how the definition of "fast" gets redefined every 18 months to to years. And how what was "fast" is now "slow".
Hands down you cannot string a rational argument against gay marriage because there isn't one. Its based on cultural fears, and intolerance. You're on the losing side of history, next to the Mississippi state police that physically assaulted my father and his friends for helping black people register to vote in early 60s. Next to KKK. And the confederates, and so on. Have fun explaining to your children or your children's children, who will grow up with gay marriage, how you were the bigot.
What?? Do you know what definition means? The definition of fast has never changed. Absolute values you might be measuring have.
Hopefully my children won't grow up with gay "marriage", they'll grow up with "marriage", and "gay marriage/union/whatever they want to call it". That's an important distinction.
You keep using the word "gay" -- are you not aware that that word has changed its meaning?
* A nun is married to God (in some religions)
* A priest is married to God (in some religions)
* A man can be married to more than one woman (in some religions)
* A woman can be married to more than one man (maybe in darkest Africa, who's to say?)
* A man can be married to a woman
* A man can be married to a tree (in India, true)
* A man can be married to a man
* A woman can be married to a woman
Why are you so sensitive about words, anyway?
Gay was defined for a long time to mean happy.
Conservative used to mean saving and preserving and conserving, instead of spending, destroying, and squandering.
Faithful used to mean good, just, and moral, instead of vituperative, devious, dim-witted, and delusional.
Words get redefined all the time. Get over it.
I don't care if gay people wish to have even more rights than me. Fine. Just don't mess about with a word that has been defined clearly for a long time.